git-find-base: add detection for possible duplicate patches

git-find-base: add detection for possible duplicate patches

Some users send a patch which includes both an attachment and inline of
the diff. This confuses git-find-base, because it will see equivalent
patch blobs. If we see the same diff hunk with identical git-index
information, print a warning, and ignore it.

This patch also rewords some of the other warnings to be more consistent
and always show the intial -> modified blobs for possible debugging.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>